If the animal is otherwise healthy and is recovering, stress free and properly nourished as well as hydrated, he should grow at least a small nub to round it off. Leopard geckos, known for tail regeneration, store fat and water in their tail, which is one of its primary purposes. Skinks use tail dropping as a defense method, not as primarily storing food, i believe. this means that regeneration isnt as vital and probably will not be significant